The present invention relates to an apparatus for stopping a truck precisely at a preselected position. In the coke oven operations, various trucks are made to run along rails laid along a battery of coke ovens. These trucks are, for example, larry cars for charging coal into the coke oven, pusher machine for pushing hot coke from the coke oven, coke guide truck, extinguisher truck and so forth. In the safe and efficient coke oven operations, it is necessary to precisely stop the truck at a preselected position in relation to a particular coke oven of the battery for the proper functioning of such trucks, e.g. charging of coal, discharging of coke and so forth.
If the stopping of the truck has to be made solely through the manual braking operation by an operator, such an operator is required to be highly trained and skilled and, even if he is highly trained and skilled, it is quite difficult to stop the truck at once precisely at the preselected position. Namely, it is necessary to repeat a minute readjustment of the position or inching, taking much labor and time. In order to obviate the above-described problem, it has been proposed and attempted to automatically stop the truck by a cooperation of an electric position detecting means and a truck driving/stopping means operative in response to the signal from the position detecting means. This attempt, however, requires a repetition of correcting operation in order to attain a sufficiently high precision of stopping, so that a longer time is required as the demand for precision becomes more severe. In addition, the undesirable phenomenon called hunting takes place to make the system practically unusable if the precision or gain is increased beyond a predetermined critical value.
Under this circumstance, Japanese Patent Publication No. 27882/73 discloses a stopping apparatus having blocks for limiting the position of stopping of the truck and laid on the floor between two rails and a pair of clamping members attached to the lower part of the truck and adapted to be operated by a pair of cylinders, respectively, to clamp one of the blocks thereby to forcibly stop the truck at the preselected position. This apparatus is advantageous in that its operation is simple and completed in quite a short period of time, but requires a complicated mechanism for retracting the clamping members to clear the blocks during running of the truck. Furthermore, a complicated electric circuit is required for the adjustment of strokes of both clamping members.